1. In a large stock pot add celery root, celery, potatoes, half the cream, and water. Bring to a boil, lower heat and simmer for an hour. Remove from heat and whisk in remaining cream and half the mascarpone. Let cool.

2. Once cooled, blend at high speed until soup is smooth. Season to taste with salt and pepper.

3. To serve, reheat soup and ladle into bowls. Place small dollop of mascarpone in center of each and drizzle with truffle oil.